7.8.1 Chapter 14: Noise and Vibration of the PEIR assesses the impact of the Project on the following types of noise:
7.8.2 Baseline noise level measurements were conducted at a number of locations relevant to the Project. Measurements were conducted continuously over a two week period.
7.8.3 The approach to assessing noise effects from the Project has focused on firstly identifying significant adverse effects that may arise and identifying mitigation measures to avoid these, and secondly identifying adverse effects that may arise that may be below the threshold for significance and identifying mitigation measures to minimise these as far as practicable. Thirdly, opportunities to reduce noise levels from the baseline case and identify improvements to the noise environment have been explored.
7.8.4 For ground noise, the current baseline noise levels have been assessed at twelve of the nearest noise sensitive receptors.
7.8.5 For air noise, modelling was carried out by the Civil Aviation Authority’s Environmental Research and Consultancy Department. Day and night noise levels were predicted using a variety of noise metrics to estimate populations and noise sensitive buildings within defined noise contours.
7.8.6 Construction would be undertaken in accordance with the Code of Construction Practice which will require contractors to adopt and implement appropriate management measures. These measures include strategies and control measures for managing the potential environmental effects of construction and limiting disturbance from construction activities as far as reasonably practicable. Where best practicable means to reduce noise on site are insufficient, noise insulation would be offered for qualifying buildings. Noise insulation or, where appropriate, temporary re-housing would avoid residents being significantly affected by levels of construction noise inside their dwellings.
7.8.7 The Project would not require a formal airspace change. This will avoid the noise impacts often associated with new flight paths. Only departures would use the northern runway, except during maintenance or emergency use as is currently the case. The majority of these would be above 1,000 feet before they leave the airfield.
7.8.8 It is proposed that the use of the northern runway would be limited to the period 06:00 hour to 23:00 hours, avoiding the majority of the more sensitive night-time period.
7.8.9 GAL would operate flights from the northern runway using procedures designed to minimise noise impacts, in line with its current processes and the commitments of the Noise Action Plan. GAL would continue to work with communities, the Noise Management Board and its aviation industry stakeholders to develop ways to minimise noise for all operations at the airport.
7.8.10 An enhanced Noise Insulation Scheme is proposed, providing greater coverage than currently offered. Residents in the highest noise Inner Zone would be offered a full package of acoustic insulation to avoid significant adverse effects, with residents in the Outer Zone being offered a lesser package but which would also include acoustic ventilation. In addition, assistance for homeowners looking to move from the most affected properties would also be provided.
7.8.11 GAL proposes a noise envelope that would set limits in terms of the areas affected by specified day and night noise levels (or contours). The identified contours have been chosen because they represent the lowest level of observable adverse effects during the day and night. Limiting noise contour areas are proposed at two points in the future as air traffic increases, with the latter being smaller than the former to ensure noise levels reduce in the longer term.
7.8.12 Mitigation for ground noise from aircraft taxiing and within the airfield has been incorporated into the design of the Project including bunding situated at the western end of northern runway, and noise barriers adjoining the bund installed at the western end of the northern runway.
7.8.13 With regards to noise from road traffic, noise barriers have been incorporated in the eastern side of the new highway to reduce the adverse effect of existing high noise levels in Riverside Garden Park and the surrounding residential area.
7.8.14 Air noise has the potential to affect residents, and other noise sensitive receptors over an area beyond the airport boundary. As aircraft age, airlines replace them with next generation aircraft so that over time the fleet transitions to next generation aircraft and, other things being equal, overall noise levels reduce. The forecasts used for the modelling of noise in the future are based on estimates of how the fleet will transition based on assumptions around airlines’ fleet procurement programmes and business models. The ‘central case’ used in the noise assessment is based on what is considered today to be the most likely rate of fleet transition. However, there is uncertainty around this, particularly at the current time due to the global pandemic and the financial impact on the airlines. Therefore air noise modelling has also been carried out for a ‘slower transition fleet’ case, based on forecasts in which the rate of fleet transition is delayed by about five years and which would result in higher noise levels than the central case.
7.8.15 The existing northern runway is currently only used when the main runway is unavailable; for example, due to maintenance work at night. In 2018, the northern runway was used by 3,543 flights, and in 2019 it was used for 2,842 flights. The Project would make alterations to the existing northern runway, resulting in increased use of this runway using the same flight paths. The smaller aircraft (below 36 metre wingspan) would use the northern runway. Consequently, any noise impacts of the Project would be the result of increases in noise due to the increased number of flights on the northern runway, rather than new noise impacts over areas previously unaffected. This would therefore avoid the noise impacts often associated with new flight paths.
7.8.16 Air noise has been assessed in 2029, 2032, 2038 and 2047 and the period of highest noise impact is expected to be the 2032 interim assessment year. At this time, the majority of effects would be in the range negligible or minor adverse to negligible or minor beneficial (not significant). The greatest noise increases are predicted mainly to the west but also to the east of the northern runway. Approximately 40 properties to the west on Ifield Road and near Russ Hill have been identified as experiencing increases of 3-6 decibels, which are potentially moderate adverse significant effects. These houses would be eligible for full noise insulation under the proposed new Noise Insulation Scheme to mitigate the potentially significant effects. For all other receptors, increases and decreases in air noise are not predicted to be significant. However, the enhanced noise insulation scheme would offer full noise insulation to homes within the new Inner Zone and a lesser package but also including acoustic ventilation to a further approximately 3,300 homes in a new Outer Zone. Noise changes at night would be lower than during the day because it is assumed that the current Night Restrictions would continue to cap aircraft numbers and noise quotas in the 23:30 to 06:00 hours period.
7.8.17 A noise envelope is proposed to set limits on noise from future operations at the airport. Noise limits are proposed for two periods, first for the period from when the northern runway opens up to when the noise impacts are expected to be greatest about three years later, and second for when the airport grows to operate at 382,000 commercial air traffic movements and thereafter.
7.8.18 Construction noise has some potential to give rise to significant effects for occupants of those properties closest to the construction works. This will be considered further during the EIA process to identify the effects more fully and to identify mitigation, to be implemented through the Code of Construction Practice.
7.8.19 Mitigation for ground noise from aircraft taxiing and within the airfield has been incorporated into the design of the Project. With this mitigation in place, levels of ground noise are not predicted to be significant for most receptors. Approximately 90 properties at Povey Cross and Charlwood and approximately 10 properties south of the airport may experience up to moderate adverse effects from ground noise. The Noise Insulation Scheme will be offered to mitigate significant effects where the noise levels exceed the significant observed effect level.
7.8.20 Remodelling of the Longbridge, North Terminal and South Terminal roundabouts and associated highways works has the potential to increase noise levels in the adjacent Riverside Garden Park and residential area. Noise barriers have been incorporated in the elevated sections of new highway to reduce the adverse effect of existing high noise levels in Riverside Garden Park and the surrounding residential area. Negligible to minor/moderate beneficial effects are predicted. Significant beneficial effects may arise in some areas.
7.8.21 With respect to cumulative effects, the majority of other development sites are located to the south of the airport. In most cases, they fall within the lower air noise contours bands, and in areas where the Project would slightly reduce air noise levels. There is potential for noise impacts on the future residents of developments as a result of Gatwick Airport’s operations, which in some cases would increase or decrease due to the Project. In seeking permission to develop sites for residential use in noisy areas developers are required to consider the potential for noise impacts on future residents and to design the developments with suitable mitigation accordingly.